There are a few guidelines that need to be  followed when deciding on a domain name:

• The entire domain name (the name and its  extension) cannot be more than 67 characters long.  That's 63 characters plus the .com (net or org).  The name must contain at least two characters, not including the extension.
• The only characters that may be used in a  domain name are letters, numerals, dashes (-) and the period (.) between the name and its  extension.
• A domain name cannot begin or end with a dash  (-)
• There can be no blank spaces within the domain name
• A name may be registered and used using any combination of upper and  lower-case letters. However, keep in mind that domain names are case-insensitive

It is most strongly advised not to try to register a domain name that contains a known trade-mark or copyrighted name or one that infringes on someone else's legal or intellectual rights.  The legal owner of a trademark has the right by law to demand the return of the name, and often does.  Also, names of some organizations or agencies, an example being the International Red Cross, are actually protected by law.